This invention relates generally to peptides useful for detecting HIV-1 antibody, and more particularly, relates to the detection of HIV-1 subtype O antibodies by utilizing an amino acid sequence of HIV-1 gp41 immunodominant region (IDR) which contains two point mutations, one at position 604 and one at position 610 of the HIV-1 subtype B gp160 sequence (the numbering is according to HIV-1 strain LAI published in Myers et al., infra).
Currently there are six recognized subtypes (so-called "clades") of HIV-1 designated as A, B, C, D, E, and F as described in Myers et al., Human Retroviruses and AIDS 1993: A Compilation and Analysis of Nucleic Acid and Amino Acid Sequences (Los Alamos National Laboratory, Los Alamos, N.M.) (1993). Recently, additional subtypes G and H have been described. See, for example, Janssens et al., AIDS Research and Human Retroviruses 10:877 (1994); and Myers et al., supra. Of emerging particular importance is the recognition of a markedly divergent group of HIV-1 sequences designated as "O". HIV-1 subtype O was first described in 1987, and was termed "O" for "outlier" because it was found to have only about 50% sequence identity at the nucleic acid level of the env gene with the other subtypes of HIV-1. These other subtypes, noted above, contain about 75% sequence identity at the nucleic acid level of the env gene with one another. The earliest reports on the sequence of O type viruses indicated that on the phylogenetic tree, SIVCPZGAB lies closer to the other HIV-1 than does group-O; i.e. this chimpanzee virus sits between group-M and group-O. See, for example, Guirtler et al., J. Virology 68:1581-1585 (1994); Vanden Haesevelde et al., J. Virology 68:1586-1596 (1994); De Leys et al., J. Virology 64:1207-1216 (1990); De Leys et al., U.S. Pat. No. 5,304,466; Gurtler et al., European Patent Publication No. 0591914A2. The group O sequences are the most divergent of the HIV-1 sequences described to date, while subtype B is the most common subtype of HIV-1.
HIV serology has been characterized in large part by the amino acid sequences of the expressed viral proteins (antigens), particularly those comprising the core and envelope. Antigens which are structurally and functionally similar but have different amino acid sequences elicit antibodies which may be similar but not identical in their specificity for antigen. One example is the antigenic difference between HIV-1 and HIV-2 gp41 IDR, which can be exploited in a variety of ways to serologically discriminate between individuals exposed to HIV-1 and/or HIV-2. See, for example, Hunt et al., AIDS Research and Human Retroviruses 6:883-898 (1990); Cmaan et al., Science 237:1346-1349 (1987); Cot et al., AIDS Research and Human Retroviruses 4:239-241 (1988); Hunt et al., U.S. Pat. No. 5,374,518. Similarly, HIV-1 group O viruses are antigenically and serologically distinguishable from other HIV-1 subtypes. Loussert-Ajaka et al., The Lancet 343:1393-1394 (1994); Gurtler et al., J. Virology 68:1581-1585 (1994); Vanden Haesevelde et al., J. Virology 68:1586-1596 (1994); De Leys et al., J. Virology 64 (supra); U.S. Pat. No. 5,304,466; Gurtler et al., E. P. O. Publication 0591914A2.
The ability to detect HIV-1 subtype 0 has become a critical concern in the blood bank community. In one study, it was reported that commercial assays capable of detecting HIV-I subtype B were not able to detect a panel of 9 samples positive for HIV-1 subtype O (I. Loussert-Ajaka et al., The Lancet 343:1393-1394 (1994)). Although the number of actual confirmed cases of infection due to HIV-1 subtype O is limited in number and geographically, there are indications that this subtype is beginning to spread from Cameroon, the initial site of the virus, to neighboring countries, such as Equatorial Guinea.
It would be advantageous to provide a reagent which could be used in an assay to detect the presence of HIV-1 subtype O antibodies in test samples.